The State Bank of Vietnam has ordered banks to sell stipulated amounts of bad debts to its asset management firm VAMC by September as part of efforts to reduce them to 3 percent.

The lenders will have to sell 75 percent of the planned total by June 30 and the rest by September 30, news website Saigon Times Online reported.

But they have all refused to reveal the amounts to be sold decided based on their bad debt levels, it said.

It is speculated to be in the trillions for some banks and hundreds of billions for others.

Central bank data shows that as of September last year the ratio had fallen to around 5.4 percent from 17 percent in September 2012.

A banker told Saigon Times Online that the more the non-performing loans the more loss provision a bank would be obliged to make, adding that a bank can further face punishment if it fails to sell enough bad debts.

The latest move shows that the central bank is getting tougher to speed up the restructure of local banks, according to the banker.

Since its establishment in July 2013, the VAMC has been criticized for tardiness in cleaning up bad debts.

As of the end of last year the company had bought bad debts worth VND137 trillion (US$6.31 billion) by issuing VND108 trillion ($4.98 billion) in special bonds, its chairman Nguyen Quoc Hung told news website VnEconomy last week.

Less than 4 percent of the purchased debts had been realized, mainly through selling them, he said.

The VAMC early this month got the green light to issue special bonds worth VND80 trillion ($3.68 billion) to banks against the bad debts it buys.